San Francisco City Attorney Dennis Herrera fired off a letter Monday to Justin Bieber's record label, Def Jam Recordings, seeking cooperation in finding, and punishing those, responsible for spray-painting city sidewalks with promotional ads for his recent album, "Purpose."

"As city attorney, I take the illegal graffiti marketed for Mr. Bieber’s album seriously, and I will aggressively pursue all available penalties and costs from those responsible for lawless marketing tactics that intend to financially benefit your respective companies," Dennis Herrera wrote in a letter to Def Jam CEO Steve Bartels and Universal Music Group's General Counsel and Executive Vice President Jeffrey Harleston.

No one has taken responsibility for the spray paint marketing campaign on city sidewalks that the public works department has described as "guerrilla marketing."

Neither Bartels in New York, nor Harleston in Santa Monica, immediately responded for comment on Monday. Bieber also did not respond to a request seeking comment via Twitter.

A modified version of sidewalk art promoting Justin Bieber's album "Purpose" is seen in San Francisco, Monday, Dec. 28, 2015.
Photo credit: Damian Trujillo/NBC Bay Area

Julie Carbone, a Montreal advertising strategist with no direct connection to the ads, said the illegal tactics, and the fines that come with it, are often worth it. She has conducted her own guerrilla campaigns, and enjoys the publicity that goes with it.

The sidewalk ads, which mostly say "Justin Bieber Purpose #Nov. 13," have been spotted as early as mid-December, in SoMa, the Mission and Upper Haight neighborhoods. They've prompted numerous complaints from residents, as the words don't easily wash away in front of their homes and businesses.

Herrerra's spokesman, Matt Dorsey, who admitted that he is a Bieber fan himself, said he doesn't know exactly how many illegally painted ads have sprouted up in the city, though his office submitted photos of at least eight pieces of evidence to Bieber's record label and attorney.

Dorsey also said didn't know exactly how much it will cost to clean up all the paint. However, the letter states the label could be liable for civil penalties of up to $2,500 for each violation. San Francisco spends about $20 million annually on graffiti prevention and removal, according to city records.

"These are visual distractions for pedestrian safety," Dorsey said Monday, standing near some Bieber graffiti on Howard Street. "And it sends a message to young people, 'Hey, if Justin Bieber does this, it's OK for you to do it.'"

Herrera's letter concluded by asking Bartels and Harleston to contact Herrera's office to "begin the process of resolving the harms done to San Francisco and its residents on your companies' behalf."

Herrera said San Francisco has a track record of penalizing companies for other ad campaigns with fines of up to six figures.

When Zynga's advertising company littered San Francisco sidewalks with stickers, Dorsey said the company paid $45,000 to clean up the mess. When IBM and NBC Universal ad campaigns, in 2001 and 2004, spray painted various logos throughout the city, Dorsey said their advertising agencies paid the city $103,000 and $100,000 respectively.